CTL responses. LCMV GP33-specific CTL responses generated by thymus-derived versus extrathymic T cells following infection with LCMV-ARM (A-D) and LCMV-WE (E). GP33 tetramer-positive CD8 T cells in the spleen (A-C) and mLNs (D) of B6 mice (control T cells; □) and OM → RAG1^-/- chimeras (extrathymic T cells; ▴) following intravenous injection of LCMV ARM (200 pfu); 3 mice per group. (B) OM → B6.SJL chimeras were created by transplantation of LckOM fetal liver into adult thymectomized-irradiated B6.SJL mice. On day 90 after transplantation these mice presented a mixed lymphoid chimerism. Kinetics of expansion of extrathymic donor-derived T cells (Ly5.2⁺; ▴) versus residual (thymus-derived) host cells (Ly5.1⁺; ▵) following LCMV infection. Six mice were tested on day 3, and 3 mice on the other days. Results are depicted as percentages of tetramer-positive CD8 T cells in panels A and B and absolute numbers in panels C and D (mean ± SD). (E) Percentage of GP33 tetramer-positive CD8 T cells in the spleen and mLNs of B6 (□; n = 3) mice and OM → RAG1-/- chimeras (▴; n = 2) 8 days following intravenous infection with LCMV-WE (200 pfu). All graphs are gated on CD8⁺ T cells.